Anaerobic transformation of phenol to benzoate via para-carboxylation: use of fluorinated analogues to elucidate the mechanism of transformation

Isomeric fluorophenols were used as phenol analogues to investigate the transformation of phenol to benzoate by an anaerobic, phenol-degrading consortium derived from freshwater sediment. Transformation of 2-fluorophenol and 3-fluorophenol led to the accumulation of fluorobenzoic acids. 2-Fluorophenol was transformed in the presence or absence of phenol, while 3-fluorophenol transformation was only observed in the presence of phenol. Identification of the resulting fluorobenzoate products as 3-fluorobenzoate and 2-fluorobenzoate isomers, respectively, together with the nontransformation of 4-fluorophenol indicated that the carboxyl group was introduced para to the phenolic hydroxyl group.